Oregon 15,000 Years B.C.

By J. D. Adams

       The Pacific Northwest is a land of contrasts, born of fire and ice, shaped by glaciers and red-hot rivers of lava. In prehistoric times, catastrophic events of fantastic scale have swept over Oregon, dimly recorded in the oldest legends of Native Americans. Foremost of these is called the Missoula Floods, in which the Willamette Valley was flooded 400 ft. deep after the release of an ice dam backing up a body of water known as Glacial Lake Missoula. The raging torrent swept down the Columbia River drainage, permanently altering the landscape in the most significant event of its kind ever recorded in geologic history.

      Ice sheets covered large areas of the northern United States during the Pleistocene Epoch, including northern Washington, Idaho, and Montana. Roughly 15,000 years ago, glacial ice grew southward into northern Idaho to block the Clark Fork River, creating 200-mile long Glacial Lake Missoula in western Montana. As the level of the lake increased, it eventually worked its way under and around the obstruction. When the ice dam gave way, a flood of unimaginable fury hurled down the Columbia Basin, scouring the topsoil from large areas of Washington and moving boulders the size of houses, some of which were carried on floating ice for many miles and deposited as glacial erratics. The torrent slowed in the Portland area, depositing huge mounds of gravel and backing up into the Willamette Valley beyond where Eugene is today. In Washington the Missoula Floods have sculpted an area known as the Channeled Scablands, containing stark canyons known as coulees, Dry Falls and numerous lakes. The damming and release of Glacial Lake Missoula occurred dozens of times over thousands of years as the ice sheet advanced. The rich soil of the Willamette Valley is the result of this repeated flooding, much of it stripped from Washington.

       Oregon’s first inhabitants, Paleolithic hunters, witnessed these Ice-Age Floods. During the Late Pleistocene Epoch, ancestors resembling modern man crossed over into North America on the Bering land bridge from Asia, possibly as long as 50,000 years ago. Dispersing into the continent, these Stone-Age nomads confronted a world of mammoths and mastodons, saber-toothed cats, and the giant bear arctodus simus, the largest North American carnivore, standing over 11 ft. on their back legs. These great beasts were examples of extreme adaptation, evolving exotic forms in the fertile land that lay south of the glaciers. During this time period, there is volcanic upheaval while glaciers recede and advance, shaping a constantly changing landscape of lakes and streams in green valleys where giant bison and ground sloths grazed. Why these animals became extinct at the end of the Pleistocene Epoch is a riddle that remains unanswered, but may involve climate changes, competition from more versatile species, and the effects of over hunting by Paleolithic inhabitants, who brought their skills and techniques from Asia.

        At the foot of glaciers that lay on the northern horizon, Oregon was a prehistoric garden where massive creatures dwelled majestically on the edge of time, never to be seen again. But the destiny of Humankind was already etched into petroglyphs from a distant dawn, with a message that we would survive and prosper. 

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